Oximation process

ABSTRACT

An improved process for oximation of carbonyl compounds, such as ketones and aldehydes by oximation with hydroxylamine including oximation processes carried out in the presence of a catalytic amount of an alkyl phenol phase transfer catalyst, such as nonylphenol or dodecylphenol and the presence of an alkali metal or alkaline earth metal compound. The resulting oximes are useful as metal extractants.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the preparation of oximes from essentiallywater insoluble carbonyl compounds, i.e. ketones or aldehydes, and inparticular to improved processes which employ a phase transfer catalyst.Hydroxyoximes prepared by the improved method are useful as metalextractants.

2. Description of Related Art

As described in U.S. Pat. No. 4,868,334, oximes are generally producedby reacting an organic carbonyl compound such as an aldehyde or ketonewith hydroxylamine, usually generated from a hydroxylamine salt such ashydroxylammonium sulfate or hydroxylammonium chloride.

Current oximation procedures, particularly of long alkyl chain ketones,employ standard oximation processes with an alcohol, such as methanol asa solvent, hydroxylammonium sulfate and sodium acetate. Since sodiumacetate must be anhydrous and is considerably more expensive than sodiumcarbonate, attempts have been made to employ sodium carbonate in theketoximation procedure, but such attempts have not been successful.

U.S. Pat. No. 4,133,834 describes the general preparation of alpha andbeta-hydroxyoximes generally useful as extractants for metals such ascopper from aqueous solutions and discusses, as exemplary processes,those of U.S. Pat. Nos. 3,449,066 and 3,592,775 relative to thepreparation of aliphatic, alpha-hydroxyoximes, from the correspondingacyloins and beta-hydroxyoximes from the corresponding aromaticphenones. In each of the processes the reaction is carried out underreflux conditions with an hydroxylamine salt in an alcohol medium (suchas methanol) in the presence of a weak base, such as sodium acetate.Such methods typically required long reaction times for completion,particularly when the oximes included aromatic groups. U.S. Pat. No.4,133,834 describes a process for reducing the time of reaction byemploying catalytic amounts of iron, Fe⁺² and Fe⁺³ Nawal K. Mathur andChander K. Narang, in "Laboratory Experiments onPhase-Transfer-Catalyzed Reactions of Neutral Molecules", J. Chem. Ed.,67, p. 273, March 1990, describe the oximation of benzophenone by firstpreparing an aqueous solution of hydroxylammonium chloride (1equiv/equiv of ketone) in water and neutralizing with sodium hydroxide(1 equiv). This results in high concentration of free hydroxylaminebeing present all at once, which in large scale operations would presentan unsafe condition. To this is added an equal volume of toluenecontaining 1 equivalent of benzophenone and 1 equivalent (stoichiometricamount) of 2-ethylhexanoic acid at 60° C. for 1.5 hour. In the reactionmixture the level of water is 53.5 moles/mole of carbonyl and the levelof toluene was 4.76 g/g of ketone. The 2-ethylhexanoic acid allegedlyacts as a bifunctional catalyst, i.e. a weak acid catalyst as well as aphase transfer catalyst.

The oximes, such as the hydroxy aryl ketoximes and hydroxy arylaldoximes, which are substantially insoluble in water but soluble inwater immiscible, organic solvents, such as kerosene, are useful insolvent extraction processes for recovery of metals, particularlycopper, from aqueous solutions. U.S. Pat. No. 4,507,268, describes anumber of such oxime reagents prepared from ketones and aldehydes, andthe use thereof in liquid/liquid extraction processes.

DESCRIPTION OF THE INVENTION

In this description, except in the operating examples or whereexplicitly otherwise indicated, all numbers describing amounts ofingredients or reaction conditions are to be understood as modified bythe word "about" in describing the broadest scope of the invention.Practice of the invention within the exact numerical limits is howevergenerally preferred.

It has now been discovered that alkyl phenols having from about 6 toabout 20, preferably about 8 to about 18 carbon atoms, when employed inthe oximation process catalyze the oximation of carbonyl containingcompounds, acting as a phase transfer catalyst, to accelerate the rateat which the carbonyl compounds, ketones or aldehydes, are oximated. Theuse of these phase transfer catalysts, provide additional unexpectedadvantages. Firstly, alcohol solvents may be avoided thereby reducingany flammability hazards, as well as eliminating environmental concernswhich normally require recovery by stripping of the methanol togetherwith the attendant cost of stripping equipment. Secondly, sodiumcarbonate may be employed in the process of oximation of the ketones,eliminating the necessity for anhydrous sodium acetate, which is notonly expensive, but which also results in the generation of acetic acidin the reaction requiring further treatment and equipment for handlingof the acetic acid. Thus, the environmental benefits of the presentinvention are many.

One aspect of the present invention accordingly provides for an improvedprocess of oximation of carbonyl compounds (ketones or aldehydes),comprising

(a) reacting a carbonyl compound with hydroxylamine in the presence of

(1) a catalytic amount of a phenol phase transfer catalyst and

(2) an alkali metal or alkaline earth metal hydroxide and carbonate(including bicarbonate) to form the oxime of said carbonyl compound; and

(b) recovering the resulting oxime from the reaction mixture.

The present invention is directed to the oximation of carbonylcompounds, and in particular to oximation of ketones or aldehydes, theoximes of which are useful in the extraction of metal values, such ascopper, from aqueous leach solutions. While the process of the presentinvention may be applied generally to the preparation of oximes ofketones or aldehydes generally, it is of particular value to thepreparation of aromatic oximes useful for extraction of metal valuesfrom aqueous solutions, which oximes are substantially insoluble inwater but are soluble in water immiscible organic solvents such askerosene, such as those described in U.S. Pat. No. 4,507,268 notedearlier above.

The present invention is useful in the preparation of hydroxy arylketoximes and aldoximes from the corresponding ketones or aldehydes.Such hydroxy aryl ketoximes and aldoximes are ideally defined byFormulas I and II ##STR1## in which R and R_(a) may be individuallyalike or different and are saturated aliphatic hydrocarbon groups of1-25 carbon atoms or an ethylenically unsaturated group of 3-25 carbonatoms and Y is H or R_(b) and R_(b) is an aliphatic hydrocarbon groupcontaining 1-10 carbon atoms; ##STR2## in which R_(a) and Y are asdefined above with respect to formula I. Preferred compounds of formulasI and II are those in which R_(a) is a straight or branched chain alkylgroup having from 7-12 carbon atoms, and wherein it is attached para tothe hydroxyl group. Among these, the more preferred are those whereinR_(a) is a mixture of isomers. Compounds of formula II which areespecially useful in the practice of metal extraction include2-hydroxy-5-heptylbenzaldoxime, 2-hydroxy-5-octylbenzaldoxime,2-hydroxy-5-nonylbenzaldoxime and 2-hydroxy-5-dodecylbenzaldoxime.Compounds of Formula I which are especially useful in the practice ofmetal extraction include 2-hydroxy-5-octylacetophenone oxime and2-hydroxy-5-nonylacetophenone oxime.

As indicated, the oxime is prepared by oximation of the correspondingketone or aldehyde with hydroxylamine. The hydroxylamine is preferablyemployed in the form of a salt thereof, preferably the sulfate, halide(chloride or bromide) or phosphate and the like. The least expensive andmost preferred is the sulfate.

The hydroxylamine, preferably the sulfate (hydroxylammonium sulfate), isemployed in an amount of at least 1 equivalent to 1 equivalent ofcarbonyl, and preferably in a slight excess up to about 15 to about 50equivalent percent, i.e. up to 1.5 equivalents of hydroxylamine tocarbonyl. Preferably, the hydroxylamine is employed in an excess amountof about 1.1 equivalent/equivalent carbonyl. Thus, the hydroxylaminewill preferably be employed in an equivalents ratio of hydroxylamine tocarbonyl greater than 1:1 up to about 1.15 or about 1.2:1 and preferablyabout 1.1:1.

The reaction of the ketone or aldehyde with hydroxylamine is carried outin the present invention in the presence of a catalytic amount of aphase transfer phenol catalyst. The preferred phenols employed as aphase transfer catalyst are those phenols having branched or straightchain alkyl groups containing from about 6 to about 20 carbon atoms,most preferably about 8 to about carbon atoms. The preferred phenolsemployed in the present invention are those containing from 8 to 12carbon atoms. The alkyl group may be a single straight chain alkyl groupor the phenol may be a mixture of branched chain isomeric alkyl groups.

The phase transfer catalyst is employed in catalytic amounts up to about0.5 moles of phenol per mole of carbonyl, preferably from about 0.05 toabout 0.3 moles phenol/mole of carbonyl, with about 0.15 to about 0.2moles phenol/mole of carbonyl being most preferred.

The reaction of the hydroxylamine with the carbonyl compound (ketone oraldehyde) is conducted in the presence of an alkali metal or alkalineearth metal hydroxide or carbonate (including bicarbonate). While sodiumcarbonate is preferred, the other alkali metal carbonates may beemployed such as potassium or lithium carbonate. Calcium carbonate ispreferred as an alkaline earth metal carbonate replacement for thesodium carbonate.

The alkaline compound is employed in at least a stoichiometric amount tothe hydroxylamine salt, i.e. at least 1 equivalent carbonate to 1equivalent hydroxylamine salt, although a slight excess is preferred upto about 15 to about 50% excess. Thus, the carbonate will preferably beemployed in an equivalent ratio of carbonate to hydroxylamine greaterthan 1:1, up to about 1.5:1, and preferably about 1.1:1.

While not intended to be limited thereto, the reaction is believed toproceed as indicated below. The phenol serves as a phase transfercatalyst and reacts at the surface of the sodium carbonate to form thesodium phenoxide and water. The sodium phenoxide can then react at thesurface of the hydroxylammonium sulfate to form sodium sulfate and thehydroxylammonium phenoxide. The resultant hydroxylammonium phenoxide issoluble in the organic phase and can react with the ketone or aldehydeto form the desired oxime, water and regenerate the phenol. The presenceof the phenolic phase transfer catalyst permits the use of lowertemperatures, while retaining reasonable time periods.

Water should be present, preferably only in an amount sufficient to wetthe surfaces of the hydroxylammonium sulfate and sodium carbonatecrystals. As Raschig hydroxylamine contains water, no added water isrequired. If none of the reactants or solvent media contain any water,where the system would otherwise be an anhydrous one, a small amount ofwater, sufficient to wet the surfaces of the hydroxylammonium sulfateand sodium carbonate crystals, will preferably be added. Accordingly,water is preferably present in the reaction mixture, either added wateror byproduct water of reaction and may be present up to an amount ofabout 10 moles of water per mole of carbonyl, preferably at least about0.1 mole water/mole of carbonyl. Preferably the water will be present inan amount of about 0.5 mole to 5 moles water/mole of carbonyl, withabout 1 mole water/equivalent carbonyl being most preferred.

The reaction may be conducted in the absence of solvent. It is, however,preferred to carry out the reaction employing a hydrocarbon solvent,such as toluene. The presence of the hydrocarbon solvent providesseveral advantages. The toluene solvent serves to thin the reactionmixture somewhat to prevent excessive foaming. The hydrocarbon solventalso promotes better dispersal of the reaction components therebyproviding further reduction in reaction time. The presence of thesolvent, such as toluene, also provides a safety feature as thetemperature may be kept fairly constant at the toluene-water azeotropereflux temperature, thereby minimizing any hazard which may beassociated with the use of hydroxylamine at high temperatures. Tolueneis the preferred hydrocarbon solvent, however other inert, aliphatic oraromatic hydrocarbon solvents may be employed, such as xylene, hexane,heptane, ethers and kerosene.

The reaction in the present invention will be complete, or substantiallycomplete in from about 1 to 7 hours, dependent on the particulartemperature of reaction. With aldehydes, such as 5-nonylsalicylaldehydeor 5-dodecylsalicylaldehyde, the operative temperature range may extendfrom ambient temperatures of about 25° C. up to about 95° C., with about50° to about 90° C. being preferred. With ketones, such as2-hydroxy-5-nonylacetophenone, the temperature will extend from about50° to about 95° with temperatures above about 60° C. being preferred,temperatures of about 75° C. to about 90° C. being the most desirable,most preferably about 90° C. With the presence of a hydrocarbon solventsuch as toluene, the reaction will be generally conducted at the refluxtemperature.

The reaction is preferably conducted with agitation (stirring) to reducethe reaction time. At preferred temperatures of 75°-90° C., withagitation, the reaction will generally be complete within about 4 toabout 6 hours. After completion of the reaction, the oxime reactionproduct is generally diluted with toluene, followed by a water wash. Thefirst water wash will be very high in salts, which may tend toprecipitate on cooling. Accordingly, until diluted, this wash watershould preferably be kept hot, i.e. 40°-50° C.

In the foregoing description, the oximation has been described employingboth a phase transfer catalyst and an alkaline compound (hydroxide,carbonate or bicarbonate). The alkaline compound is employed preferablyin a buffering capacity in a hydrocarbon solvent such as those earlierdescribed, although the reaction may be conducted in the absence ofhydrocarbon solvent. Again water is present in amounts as earlierdescribed above. This aspect of the invention is particularly applicableto the preparation of 5-alkylsalicylaldoximes from the correspondingaldehydes in which the alkyl groups have from about 6 to about 12 carbonatoms, preferably about 8 to about 12 carbon atoms.

Accordingly, this invention is particularly adapted to a process for thepreparation of alkylsalicylaldoximes in which the alkyl group containsfrom about 6 to about 12 carbon atoms comprising:

(i) reacting an alkylsalicylaldehyde in which the alkyl groups containfrom about 6 to about 12 carbon atoms with hydroxylamine in the presenceof

(x) an alkaline compound selected from the group of an alkali metal oralkaline earth metal hydroxide, carbonate and bicarbonate, and

(y) water in an amount sufficient to wet the surfaces of thehydroxylamine and the alkaline compound; and

(ii) recovering the resulting oxime from the reaction mixture.

The earlier description in relation to oximation of aldehydes as to thereactants, amounts and conditions of reaction apply. The preferredsalicylaldehydes are the heptyl, octyl, dodecyl and most preferably thenonylsalicylaldehyde. The preferred hydroxylamine source ishydroxylamine sulfate and the preferred alkaline compounds are sodiumhydroxide or sodium carbonate. Where a hydrocarbon solvent is employed,toluene is preferred. The preferred temperature of reaction is fromabout 60° to about 90° C. The preferred amounts of the materials are thesame as earlier described.

To further illustrate the various objects and advantages of the presentinvention, the following example is provided in which all parts andpercentages are by weight unless otherwise indicated. It is understoodthat the example is entirely illustrative and in no way intended tolimit the scope of the invention.

EXAMPLE

To exemplify the invention, the preparation of dodecylsalicylaldoxinefrom dodecylsalicylaldehyde is illustrated by the following, in whichdodecylphenol was employed as the phase transfer catalyst. Forcomparison the identical reaction was carried out in the absence of thedodecylphenol phase transfer catalyst.

In the reaction, employed was a mixture of 100 grams of5-dodecylsalicylaldehyde; 25 ml. of toluene; 28.7 grams of hydoxylaminesulfate; 18.53 grams of sodium carbonate and 5.3 ml. of water. Themixture was stirred at ambient temperature (25°-28° C) with a paddlestirrer at 1000 rpm.

An identical reaction mixture was employed with 15 grams ofp-dodecylphenol added. Again the mixture was stirred at ambienttemperature with a paddle stirrer at 1000 rpm.

Samples were periodically withdrawn, diluted with toluene, washed withwater and stripped of volatiles. The resulting samples were thenanalyzed by infra red to determine the amount of dodecylsalicylaldehyde(DSA) in the sample. The following results reported on a % weight/volume(w/v%) illustrate the decreasing amount of the aldehyde in the samples.

                  TABLE I                                                         ______________________________________                                        Time     Added dodecylphenol                                                                          No added phenol                                       ______________________________________                                        1 hr..sup.                                                                                 74 w/v %   94.5 w/v %                                            2 hrs.   61             89                                                    3 hrs.   45             78                                                    8 hrs.   33             49                                                    24 hrs.   9             15.5                                                  ______________________________________                                    

The foregoing illustrates the acceleration of the reaction using aphenol as a phase transfer catalyst, even at ambient temperatures. Athigher temperatures preferably 60° to 90° C., the times to completereaction would be less than 7 hours. While the dodecylphenol wasemployed with oximation of dodecylsalicylaldehydes so that the alkylgroup in the aldehyde being oximated was the same as the alkyl group ofthe phenol, it is not necessary that the two groups correspond. Thus adodecylphenol may be employed to oximate aldehydes containing a heptyl,octyl or nonyl group. Correspondingly, a heptyl, octyl or nonyl phenolmay be employed in catalyzing oximation of dodecylsalicylaldehyde. Inthis regard, when the aldehyde itself is prepared from a phenol,residual phenol from the aldehyde preparation may be retained in thealdehyde product and be used as the phase transfer catalyst duringoximation. If a different alkyl group phenol is to be employed as thephase transfer catalyst, it is, of course added to the reaction mixtureprior to reaction.

We claim:
 1. In a method of preparing aromatic oximes by reaction of anaromatic ketone or aldehyde carbonyl compound with hydroxylamine theimprovement which comprises conducting the reaction in the presence of acatalytic amount of an alkyl phenol, and an alkali metal or alkalineearth metal hydroxide, carbonate or bicarbonate, the alkyl phenol beingpresent in an amount effective to act as a phase transfer catalyst.
 2. Amethod as defined in claim 1 wherein the carbonyl compound is selectedfrom the group consisting of heptylsalicylaldehyde, octylsalicylaldehydenonylsalicylaldehyde and dodecylsalicylaldehyde.
 3. A method as definedin claim 1 wherein said phenol phase transfer catalyst is an alkylphenol in which the alkyl group has from about 6 to about 20 carbonatoms.
 4. A method as defined in claim 3, wherein said alkyl phenolcontains from about 8 to about 18 carbon atoms in the alkyl groups.
 5. Amethod as defined in claim 3, wherein the alkyl phenol phase transfercatalyst is present in an amount of about 0.05 to about 0.3 moles ofphenol per mole of carbonyl.
 6. A method as defined in claim 5 whereinthe alkyl phenol catalyst is present in an amount of about 0.15 to about0.2 moles of phenol per mole of carbonyl.
 7. A method as defined inclaim 1, wherein said carbonate is sodium carbonate.
 8. A method asdefined in claim 7, wherein said carbonate is present in at least astoichiometric amount to the hydroxylamine.
 9. A method as defined inclaim 8 wherein said carbonate is present in an amount of 1.1equivalents of carbonate to 1 equivalent hydroxylamine.
 10. A method asdefined in claim 1, wherein said carbonyl compound isdodecylsalicylaldehyde and said alkyl phenol phase transfer catalyst isdodecylphenol.
 11. A method as defined in claim 1, wherein said carbonylcompound is nonylsalicylaldehyde and said alkylphenol phase transfercatalyst is nonylphenol.
 12. A method as defined in claim 1, wherein thewater content is from about 0.1 to about 10 moles of water per mole ofcarbonyl.
 13. A method as defined in claim 12, wherein said reaction isconducted in a non-alcoholic media containing water in an amount justsufficient to wet the surfaces of the hydroxylamine and carbonatereactants.
 14. A method as defined in claim 12, wherein the mediafurther comprises a hydrocarbon solvent.
 15. A method as defined inclaim 14, wherein said hydrocarbon solvent is toluene.
 16. A method asdefined in claim 12, wherein said carbonyl compound is selected from thegroup consisting of 2-hydroxy-5-octylacetophenone,2-hydroxy-5-nonylacetophenone, 5-nonylsalicylaldehyde,5-octylsalicylaldehyde and 5-dodecylsalicylaldehyde and2-hydroxy-5-dodecylacetophenone.
 17. A method as defined in claim 8,wherein the carbonyl compound is or 5-nonylsalicylaldehyde or5-dodecylsalicylaldehyde, said alkyl phenol phase transfer catalyst isan alkyl phenol in which the alkyl group contains from about 8 to about12 carbon atoms present in an amount of about 0.15 to about 0.2 moles ofphenol per mole of carbonyl, the hydroxylamine is hydroxylammoniumsulfate present in an amount of about 1.1 equivalents to 1 equivalentcarbonyl, said carbonate is sodium carbonate present in an amount ofabout 1.1 equivalents carbonate to 1 equivalent of hydroxylamine and thereaction is conducted at a temperature of greater than about 35° C. upto about 90° C.
 18. A method of preparing a hydroxy oxime having theformula ##STR3## in which R and R_(a) may be individually alike ordifferent and are saturated aliphatic hydrocarbon different and aresaturated aliphatic hydrocarbon groups of 1-25 carbon atoms orethylenically unsaturated groups of 3-25 carbon atoms and Y is H orR_(b) where R_(b) is an aliphatic hydrocarbon group containing from 1 toabout 10 carbon atoms; ##STR4## in which R_(a) and Y are as defined withrespect to Formula I, comprising(a) reacting a carbonyl compoundcorresponding to the hydroxy oxime defined above with hydroxylamine inthe presence of(1) a catalytic amount of an alkyl phenol phase transfercatalyst and (2) an alkali metal or alkaline earth metal hydroxide,carbonate or bicarbonate whereby the carbonyl group of the carbonylcompound is converted to the oxime group; and (b) recovering theresulting oxime from the reaction mixture.
 19. A method as defined inclaim 18 wherein said phase transfer catalyst is an alkyl phenolcontaining from about 6 to about 20 carbon atoms in the alkyl group andthe alkyl phenol is present in an amount of about 0.05 to about 0.5moles of phenol per mole of carbonyl, the hydroxylamine reactant ishydroxylammonium sulfate present in an amount of about 1.1 equivalentsper equivalent of carbonyl, said carbonate is sodium carbonate presentin an amount cf about 1.1 equivalents carbonate to 1 equivalent ofhydroxylamine, and the reaction is conducted at about 50° to about 90°C. in the presence of water in a sufficient amount to wet the surfacesof the hydroxylammonium sulfate and the carbonate.
 20. A method asdefined in claim 19, wherein the phase transfer catalyst is an alkylphenol having from about 8 to about 12 carbon atoms in the alkyl grouppresent in an amount of about 0.1 to about 0.2 moles of phenol perequivalent of carbonyl, and in which the alkyl group of the alkylphenolis the same as, or different from, R_(a) and the reaction is conductedwith agitation at a temperature of about 90° C. in a non-alcoholic,hydrocarbon solvent reaction media for at least about 1 hour.
 21. Amethod as defined in claim 20, wherein said hydrocarbon solvent istoluene.